1. Technical Field
The present invention relates to a semiconductor device in which an air gap is provided between an interconnect and an insulating film having the interconnect provided therein and a method of manufacturing a semiconductor device.
2. Related Art
With the reduction in size of semiconductor devices, the gap between interconnects has been reduced. When the gap between the interconnects is reduced, the capacitance between the interconnects is increased, which causes a signal delay. As an example of a technique for reducing the capacitance between the interconnects, an air gap is provided between the interconnect and an insulating film having the interconnect provided therein.
U.S. Patent Application Publication No. 2008/0076258 discloses a method as follows. When a trench for burying an interconnect is formed in an insulating film, a deteriorated layer is formed on the side wall of the trench. The deteriorated layer is removed after the interconnect is formed, thereby forming an air gap between the interconnect and the insulating film.
Japanese Unexamined Patent Publication No. 2008-300652 discloses a method as follows. First, catalytic characteristic film is formed on the bottom and the side of a trench which is filled up a Cu film to make the interconnect. Next, the catalytic characteristic film on the side of the trench is removed so as to form an air gap between the interconnect and the insulating film.
Japanese Unexamined Patent Publication No. 2008-205458 discloses a method as follows which is not a technique for forming an air gap. First, A metal cap is formed over an interconnect. Next, an surface of an insulating film having the interconnect is damaged, and the damaged surface is removed.
Inventor finds out an problem as follows. As shown in FIG. 9A, when a via 421 and an interconnect trench 422 are formed in an interconnect layer 420 that is provided on an interconnect layer 400 having an air gap 402 formed therein, the positional deviation between the via 421 and the interconnect 404 of the interconnect layer 400 occurs. An opening region 424 that is connected to an upper part of the air gap 402 is formed on the bottom of the via 421 according to the degree of the positional deviation. In the structure in which the opening region 424 is formed, as shown in FIG. 9B, when a diffusion barrier metal film 430 and a seed film 432 are formed in the via 421 and the interconnect trench 422, the diffusion barrier metal film 430 and the seed film 432 are not formed in and around the opening region 424. As a result, a void 426 is formed in an interconnect 434. Therefore, it is necessary to prevent a region that is connected to the air gap 402 from being formed on the bottom of the via 421 even when the positional deviation between the interconnect 404 and the via 421 occurs.